1. Field of the Invention
This invention relates to a picture processor and more particularly a semiconductor memory for use in video signal processing.
2. Description of the Prior Art
Conventional semiconductor memories for use in picture processing are known, as for example, a video random access memory (V-RAM), field memory and line memory, all of which are produced commercially. Each of these forms of memories is of the type in which video data is written thereinto and, after being subjected to desired processing, readout therefrom.
With respect to a V-RAM, as the term represents, video data can be randomly read from or written into such a memory for complex video signal processing, and a graphic display can be performed. The feature of randomly processing all bits, however, makes the V-RAM relatively complicated in providing for the control of address signals for identifying individual bits therein. Furthermore, externally supplied address signals require more address pins in an integrated circuit assembly of a V-RAM structure. This aspect adds to the difficulty in the manufacture of high packaging density circuit boards.
On the other hand, it would be desirable for image reproduction TV and VTR to employ memory devices permitting video data processing with minimal control signals for achieving higher packaging density on a circuit board as opposed to a random access function obtained through the use of a V-RAM structure. To this end, field memory and line memory structures have been developed. Generally, a field memory is used for a still picture, double speed or slow reproduction images. A line memory is useful in improving the picture quality (drop out correction), time base corrector (jitter correction), interlace (interlaced scanning) to non-interlace (sequential scanning) conversion, etc. Field memories and line memories perform their functions in the storage of video data and the accessing thereof without needing external address signals, which is reflected in a smaller number of control signals being involved in the processing of video data stored therein, and consequently a reduction in the number of pins required in an integrated circuit package incorporating such memory structures. Thus, a higher package density and a smaller-size circuit board can be realized with such memory structures. However, no success has been achieved with field and line memories in video data processing toward the realization of characters-in-picture or still picture-in-picture on a TV display screen.